Dual-fuel heater

ABSTRACT

According to one implementation a dual-fuel wall heater is provided that comprises a gas burner suitable for receiving a first gas or a second gas, a first pilot burner adapted to the first gas and a second pilot burner adapted to the second gas. The heater includes at least one pressure regulator, a control valve in fluid communication with the pressure regulator, and a selector valve in fluid communication with a gas outlet of the control valve. Each of the first and second pilot burners is arranged to direct a flame toward respective first and second thermocouples. The control valve includes an electromagnetic valve electrically connected to both the first and second thermocouples, the first and second thermocouples being arranged electrically connected in reverse polarity, such that in the event of the second gas being improperly supplied to the first pilot burner the resulting electromotive force generated by the first and second thermocouples is less than a disengagement threshold value of the electromagnetic valve.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application relates to and claims the benefit and priority to Spanish Patent Application No. P201730329, filed Mar. 15, 2017.

TECHNICAL FIELD

The present invention relates to a dual-fuel heater.

BACKGROUND

Dual-fuel wall heaters suitable for receiving natural gas or liquid propane gas are known in the prior art. Said heaters comprise a main burner and two pilot burners adapted to the first gas or second gas, respectively. The heater further comprises at least one pressure regulator regulating the pressure at which the incoming gas exits said regulator, and a control valve communicated with the pressure regulator.

In addition, wall unvented heaters include, for the sake of safety, oxygen depletion systems adapted to each gas, such that when one of the oxygen depletion systems detects a drop in the amount of oxygen in the environment below 18%, the control valve shuts off the passage of gas towards the burner and to the pilot burners.

US2012/0067341A1 discloses a unvented dual-fuel wall heater further comprising a selector communicated with the control valve, with the oxygen depletion systems and with the burner, and being suitable for being positioned in a first position in which it allows the passage of gas towards the first pilot burner and towards the burner, or in a second position in which it allows the passage of gas towards the burner but preventing the passage of gas towards the first pilot burner. Regardless of the position of the selector, the gas circulates towards the second oxygen depletion system. Each oxygen depletion system comprises a pilot burner and a thermocouple.

For the purpose of detecting gas supply errors, the heater incorporates a thermal switch electrically connected with the oxygen depletion systems through a thermal control block. When the operator supplies a gas other than the one selected in the selector, the thermal switch sends a signal to the control valve when a given temperature in the burner is exceeded to shut off the passage of gas.

SUMMARY OF THE DISCLOSURE

The heater of the invention comprises a gas burner suitable for receiving a first gas or a second gas, a first pilot burner adapted to the first gas, a second pilot burner adapted to the second gas, and at least one pressure regulator including a gas inlet and a gas outlet, and being suitable for regulating at the gas outlet the pressure of the first gas supplied at a first pressure to the gas inlet or the pressure of the second gas supplied to the gas inlet at a second pressure.

The heater further comprises a control valve communicated with the pressure regulator, a selector communicated with the control valve through a first conduit, with the first pilot burner through a second conduit and with the burner through a third conduit, the selector being suitable for being positioned in a first position in which it allows the passage of gas towards the first pilot burner, or in a second position in which it prevents the passage of gas towards the first pilot burner, and the first conduit being communicated with the second pilot burner through a fourth conduit, such that regardless of the position of the selector, the first or second gas circulates through the first conduit and through the fourth conduit towards the second pilot burner.

Furthermore, the first pilot burner comprises a first thermocouple and the second pilot burner comprises a second thermocouple, and the control valve comprises an electromagnetic valve electrically connected with the first thermocouple and the second thermocouple, the first thermocouple and the second thermocouple being arranged electrically connected to one another in reverse polarity, such that in the event of the second gas being supplied when the selector is positioned in the first position, the resulting electromotive force generated by the first thermocouple and the second thermocouple is less than a disengagement threshold value after which the electromagnetic valve is disengaged.

A simplified dual-fuel wall heater with a safety system in the event of gas supply errors is thereby obtained, given that in the event of the wrong gas, i.e. the gas that was not selected in the selector, being supplied, the electromagnetic valve does not become disengaged such that it shuts off the passage of gas towards the selector and towards the second pilot burner.

These and other advantages and features will become evident in view of the drawings and detailed description.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of an embodiment of a dual-fuel wall heater.

FIG. 2 is a schematic view of the connections of the dual-fuel wall heater shown in FIG. 1.

FIG. 3 is a schematic view of the connections of a second embodiment of the dual-fuel wall heater.

FIG. 4 shows a detailed front view of the electrical connection and the fluid communication of the first and second pilot burner with the control valve and the selector valve.

FIG. 5 shows a detailed front view of the first and second pilot burner of FIG. 4, natural gas being supplied to the control valve and the selector valve in position A.

FIG. 6 shows a detailed front view of the first and second pilot burner of FIG. 4, liquefied petroleum gas being supplied to the control valve and the selector valve in position B.

FIG. 7 shows a detailed front view of the first and second pilot burner of FIG. 4, natural gas being supplied to the control valve and the selector valve in position B.

FIG. 8 shows a detailed front view of the first and second pilot burner of FIG. 4, liquefied petroleum gas being supplied to the control valve and the selector valve in position A.

DETAILED DESCRIPTION

FIG. 1 shows a dual-fuel wall heater 1 (hereinafter heater 1) comprising a burner 2 suitable for receiving a first gas or a second gas, a first pilot burner 17 suitable for receiving the first gas and a second pilot burner 22 suitable for receiving the second gas.

In the embodiments shown in the drawings, the first gas is natural gas and the second gas is liquefied petroleum gas (also known as LPG). In other embodiments, the first gas is natural gas and the second gas is butane.

In the embodiments shown in FIGS. 2 and 3, each pilot burner 17 and 22 comprises a pilot injector 19 and 23, a piezo igniter 21 and 24, and a thermocouple 20 and 25. The pilot injectors 19 and 23 are arranged close to the outer surface of the burner 2. The piezo igniters 21 and 24 are arranged adjacent to the respective pilot injector 19 and 23, and the thermocouples 20 and 25 are arranged close to the corresponding pilot injectors 19 and 23. Each pilot burner 17 and 22 is fixed to the heater 1 through a respective support 45 and 46.

The heater 1 further comprises a pressure regulator 3 including a gas inlet 4 and a gas outlet 5. The pressure regulator 3 is suitable for regulating at the gas outlet 5 the pressure of the first gas supplied at a first pressure to the gas inlet 4 or the pressure of the second gas supplied to the gas inlet 4 at a second pressure.

The heater 1 also comprises a control valve 6 communicated with the pressure regulator 3. The control valve 6 includes a gas inlet 7 communicated with the gas outlet 5 of the pressure regulator 3 through a conduit 30 and a gas outlet 8. The control valve 6 further comprises an electromagnetic valve 26 electrically connected with the first thermocouple 20 and with the second thermocouple 25 and suitable for shutting off the passage of gas through the gas outlet 8.

In addition, the heater 1 comprises a selector 10 suitable for being positioned in a first position A, in which it allows the passage of gas towards the first pilot burner 17 and towards the burner 2, or in a second position B, in which it allows the passage of gas only towards the burner 2, preventing the passage of gas towards the first pilot burner 17.

The selector 10 comprises a gas inlet 9 communicated with the gas outlet 8 of the control valve 6 through the first conduit 31, a first gas outlet 11 communicated with the pilot injector 19 of the first pilot burner 17 through a second conduit 32, and a second gas outlet 12 communicated with a first injector 40 of the burner 2 through a third conduit 34. In the embodiments schematically shown in FIGS. 2 and 3, the first conduit 31 is communicated with the second pilot burner 22 through a fourth conduit 33, such that regardless of the selector 10 being positioned in position A or in position B, at least part of the gas circulating through the first conduit 31 circulates through the fourth conduit 33 towards the pilot injector 23 of the pilot burner 22. The second pilot burner 22 is therefore ignited in a continuous manner while there is a gas supply.

In the embodiments shown in FIGS. 2 and 3, the burner 2 comprises two injectors. The first injector 40 is adapted to the first gas and is communicated with the selector 10 through the third conduit 34, whereas the second injector 41 is adapted to the second gas and is communicated with the selector 10 through a fifth conduit 35. Both injectors 40 and 41 are arranged close to the plurality of openings 43 comprised in the burner 2. Both injectors 40 and 41 are arranged fixed to the heater 1 through a support 42 shown in FIG. 1.

In addition, the heater 1 allows shutting off the passage of gas through the control valve 6 in the event that a first gas or a second gas has been selected but the wrong gas is supplied. To that end, the first thermocouple 20 and the second thermocouple 25 are arranged electrically connected to one another in reverse polarity, such that in the event of the second gas being supplied when the selector 10 is positioned in the first position A, the resulting electromotive force generated by the first thermocouple 20 and the second thermocouple 25 is less than a disengagement threshold value of the electromagnetic valve and therefore, the electromagnetic valve 26 shuts off the passage of gas. Disengagement threshold value is understood as the minimum disengagement value below which disengagement of the electromagnetic valve 26 is assured.

FIG. 4 shows a detailed front view of the electrical connection and the fluid communication of the first and second pilot burner 17, 22 with the control valve 6 and the selector 10. In the event that the selector 10 is positioned in position A, and LPG gas is supplied instead of natural gas NG through the pressure regulator 3, as shown in FIG. 8 where liquefied petroleum gas LPG is supplied to the control valve 6, some of the LPG gas will circulate towards the pilot injector 23 of the second pilot burner 22 (calibrated for LPG gas), some will circulate towards the pilot injector 19 of the first pilot burner 17 and some will circulate towards the burner 2. Since the pilot injector 19 of the first pilot burner 17 is calibrated for natural gas, the outlet diameter is greater than that of the injector calibrated for LPG gas, so the flame generated in the pilot injector 19 is large. Since both thermocouples 20 and 25 are connected in reverse polarity, the currents generated by each of them conflict with one another such that the resulting electromotive force is less than the disengagement threshold value of the electromagnetic valve 26, disengagement threshold value being understood as the electromotive force value below which it is assured that the electromagnetic valve 26 is disengaged and, therefore, shuts off the passage of gas. In the embodiments shown, the disengagement threshold value is about 1 mV. In addition, the engagement threshold value of said electromagnetic valve is about 4 mV, therefore, the ratio of the engagement threshold value to the disengagement threshold value is about 4:1. Values exceeding 1 mV do not assure stable disengagement (and therefore the closure) of the electromagnetic valve 26.

In the event that the selector is positioned in position B, i.e., in the LPG gas position, and natural gas is supplied through the pressure regulator 3, as shown in FIG. 7 where natural gas NG is supplied to the control valve 6, said natural gas will only circulate towards the pilot injector 23 of the second pilot burner 22 and towards the burner 2 given that the selector 10 blocks the passage towards the pilot injector 19 of the first pilot burner 17. Since the pilot injector 23 of the second pilot burner 22 is calibrated for LPG gas, the outlet diameter is less than that calibrated for natural gas, so the flame generated in the pilot injector 23 upon passage of natural gas is small and does not heat the corresponding thermocouple 25 enough for the electromagnetic valve 26 to become engaged. In other words, the current generated by the thermocouple 25 is less than that required to generate an electromotive force exceeding the engagement threshold value of the electromagnetic valve 26, so the electromagnetic valve 26 remains closed and there is no passage of gas from the control valve 3 towards the pilot burners 19 and 23 or towards the burner 2.

In addition, in the event that the selector is positioned in position A, i.e., in the natural gas position, and natural gas is supplied through the pressure regulator 3, as shown in FIG. 5, some of the natural gas will circulate towards the pilot injector 23 of the second pilot burner 22, some will circulate towards the pilot injector 19 of the first pilot burner 17 and some will circulate towards the burner 2. As explained above, in this case the flame generated in the pilot injector 23 is small and therefore the corresponding thermocouple 25 does not heat up as much as thermocouple 20 of the first pilot burner 17 does as a result of the flame generated in the pilot injector 19 of the first pilot burner 17. The current generated in the thermocouple 25 of the second pilot burner 22 is less than that generated by the thermocouple 20 of the first pilot burner 17, and the resulting electromotive force exceeds the engagement threshold value, so the electromagnetic valve 26 continues open and the passage of gas towards the pilot injectors 19 and 23 and the burner 2 also is allowed.

In the event that the selector is positioned in position B, i.e., in the LPG position, and liquefied petroleum gas LPG is supplied through the pressure regulator 3, as shown in FIG. 6, the LPG gas will circulate towards the pilot injector 23 of the second pilot burner 22, and some will circulate towards the burner 2. In this case the flame generated in the pilot injector 23 heats up the corresponding thermocouple 25 of the second pilot burner 22. The current generated in the thermocouple 25 of the second pilot burner 22 results in an electromotive force exceeding the engagement threshold value, so the electromagnetic valve 26 continues open and the passage of gas towards the pilot injector 23 and the burner 2 also is allowed.

FIG. 3 shows a second embodiment of the invention, wherein the first thermocouple 20 and the second thermocouple 25 are connected to one another and with the electromagnetic valve 26 in parallel. The operation is similar to that described in the first embodiment.

In other embodiments not shown, the dual-fuel wall heater can comprise two distributors communicated with the control valve. The burner may in turn include a single injector instead of the two described, without modifying the invention.

Finally, in other embodiments not shown in the drawings, the dual-fuel wall heater can be an unvented heater, so the gas supply towards the burner must be cut off when it is detected that the oxygen level drops below 18%. In that case, the first pilot injector 19 is calibrated for the first gas and the second pilot injector 23 is calibrated for the second gas with such precision that both pilot injectors 19 and 23 generate a stable flame insofar as the oxygen level in the room is suitable, but in the event that the oxygen level starts to drop, they generate a flame that is separated from the corresponding pilot injector 19 and 23. When the oxygen level is less than 18%, the flame generated through the respective pilot injector 19 and 23 is so separated from the corresponding pilot injector 19 and 23 that it does not heat up the corresponding thermocouple 20 and 25, such that the thermocouple stops generating the electromotive force required to keep the electromagnetic valve 26 engaged, said electromagnetic valve 26 shutting off the passage of gas. The pilot burner including the injector calibrated in this sense is known as an oxygen depletion system or ODS. 

What is claimed is:
 1. A dual-fuel heater comprising: a main gas burner configured to receive and burn a first gas or a second gas, the main gas burner comprising an injector through which the first or second gases are delivered to the main gas burner; a first pilot burner assembly including a first pilot burner and a first thermocouple, the first pilot burner configured to receive and burn the first gas to produce a flame directed at the first thermocouple; a second pilot burner assembly including a second pilot burner and a second thermocouple, the second pilot burner configured to receive and burn the second gas to produce a flame directed at the second thermocouple; a pressure regulator that includes a gas inlet and a gas outlet, the pressure regulator being configured to regulate at the gas outlet a pressure of the first gas supplied at a first pressure to the gas inlet or to regulate at the gas outlet a pressure of the second gas supplied at a second pressure to the gas inlet; a control valve having a gas inlet in fluid communication with the gas outlet of the pressure regulator, the control valve having a gas outlet, the control valve comprising an electromagnet valve, the first thermocouple electrically coupled to the electromagnet valve, the second thermocouple electrically coupled to the electromagnet valve, the electromagnetic valve having an engagement threshold voltage value at which the electromagnet valve transitions from a closed position to an open position and a disengagement threshold voltage value at which the electromagnetic valve transitions from an open position to a closed position; a gas conduit in fluid communication with the gas outlet of the control valve, the second pilot burner being continuously in fluid communication with the gas conduit; a selector valve having a gas inlet, a first gas outlet in fluid communication with the first pilot burner and a second gas outlet in fluid communication with the injector of the main gas burner, the gas inlet of the selector valve being in fluid communication with the gas conduit, the selector valve having a first position in which fluid communication of the gas inlet of the selector valve with the first pilot burner is enabled and in which fluid communication between the gas inlet of the selector valve with the main gas burner injector is enabled, the selector valve having a second position in which fluid communication of the gas inlet of the selector valve with the first pilot burner is prevented and in which fluid communication between the gas inlet of the selector valve with the injector of the main gas burner is enabled, there being fluid communication between the gas outlet of the pressure regulator and the second pilot burner when the selector valve is in both the first and second positions; the first thermocouple and the second thermocouple being arranged electrically connected to one another in reverse polarity such that in the event of the second gas being supplied to the first pilot burner, a resulting voltage generated by the first thermocouple and the second thermocouple is equal to or less than the disengagement threshold voltage value.
 2. The dual-fuel heater according to claim 1, wherein the first gas is natural gas and the second gas is liquefied petroleum gas.
 3. The dual-fuel heater according to claim 1, wherein the first gas is natural gas and the second gas is butane gas.
 4. The dual-fuel heater according to claim 1, wherein the first thermocouple and the second thermocouple are connected to one another and with the electromagnetic valve in series.
 5. The dual-fuel heater according to claim 1, wherein the first thermocouple and the second thermocouple are connected to one another and with the electromagnetic valve in parallel.
 6. The dual-fuel heater according to claim 1, wherein the ratio of the engagement threshold voltage value to the disengagement threshold voltage value of the electromagnetic value is at least 4 to
 1. 7. The dual-fuel heater according to claim 1, wherein the first pilot burner and the first thermocouple function as a first oxygen depletion sensor and the second pilot burner and the second thermocouple function as a second oxygen depletion sensor.
 8. The dual-fuel heater according to claim 7 wherein when the selector valve is in the first position to which the first gas is delivered to both the first and second pilot burners, the first thermocouple produces a voltage that is equal to or greater than the engagement threshold voltage value.
 9. The dual-fuel heater according to claim 7, wherein when the selector valve is in the second position and the second gas is delivered only to the second thermocouple, the second thermocouple produces a voltage that is equal to or greater than the engagement threshold voltage value.
 10. The dual-fuel heater according to claim 1, wherein the engagement threshold value is about 4 mV.
 11. The dual-fuel heater according to claim 1, wherein the disengagement threshold value is about 1 mV.
 12. A dual-fuel heater comprising: a main gas burner configured to receive and burn a first gas or a second gas, the main gas burner comprising a first injector through which the first gas is delivered to the main gas burner and a second injector through which the second gas is delivered to the main gas burner; a first pilot burner assembly including a first pilot burner and a first thermocouple, the first pilot burner configured to receive and burn the first gas to produce a flame directed at the first thermocouple; a second pilot burner assembly including a second pilot burner and a second thermocouple, the second pilot burner configured to receive and burn the second gas to produce a flame directed at the second thermocouple; a pressure regulator that includes a gas inlet and a gas outlet, the pressure regulator being configured to regulate at the gas outlet a pressure of the first gas supplied at a first pressure to the gas inlet or to regulate at the gas outlet a pressure of the second gas supplied at a second pressure to the gas inlet; a control valve having a gas inlet in fluid communication with the gas outlet of the pressure regulator, the control valve having a gas outlet, the control valve comprising an electromagnet valve, the first thermocouple electrically coupled to the electromagnet valve, the second thermocouple electrically coupled to the electromagnet valve, the electromagnetic valve having an engagement threshold voltage value at which the electromagnet valve transitions from a closed position to an open position and a disengagement threshold voltage value at which the electromagnetic valve transitions from an open position to a closed position; a gas conduit in fluid communication with the gas outlet of the control valve, the second pilot burner being continuously in fluid communication with the gas conduit; a selector valve having a gas inlet, a first gas outlet in fluid communication with the first pilot burner, a second gas outlet in fluid communication with the first injector of the main gas burner and a third gas outlet in fluid communication with the second injector of the main gas burner, the gas inlet of the selector valve being in fluid communication with the gas conduit, the selector valve having a first position in which fluid communication of the gas inlet of the selector valve with the first pilot burner and the first injector of the main burner is enabled and in which fluid communication between the gas inlet of the selector valve with the second injector of the main gas burner is prevented, the selector valve having a second position in which fluid communication of the gas inlet of the selector valve with the first pilot burner and the first injector of the main gas burner is prevented and in which fluid communication between the gas inlet of the selector valve with the second injector of the main gas burner is enabled, there being fluid communication between the gas outlet of the pressure regulator and the second pilot burner when the selector valve is in both the first and second positions; the first thermocouple and the second thermocouple being arranged electrically connected to one another in reverse polarity such that in the event of the second gas being supplied to the first pilot burner, a resulting voltage generated by the first thermocouple and the second thermocouple is equal to or less than the disengagement threshold voltage value.
 13. The dual-fuel heater according to claim 12, wherein the first gas is natural gas and the second gas is liquefied petroleum gas.
 14. The dual-fuel heater according to claim 12, wherein the first gas is natural gas and the second gas is butane gas.
 15. The dual-fuel heater according to claim 12, wherein the first thermocouple and the second thermocouple are connected to one another and with the electromagnetic valve in series.
 16. The dual-fuel heater according to claim 12, wherein the first thermocouple and the second thermocouple are connected to one another and with the electromagnetic valve in parallel.
 17. The dual-fuel heater according to claim 12, wherein the ratio of the engagement threshold voltage value to the disengagement threshold voltage value of the electromagnetic value is at least 4 to
 1. 18. The dual-fuel heater according to claim 12, wherein the first pilot burner and the first thermocouple function as a first oxygen depletion sensor and the second pilot burner and the second thermocouple function as a second oxygen depletion sensor.
 19. The dual-fuel heater according to claim 18, wherein when the selector valve is in the first position to which the first gas is delivered to both the first and second pilot burners, the first thermocouple produces a voltage that is equal to or greater than the engagement threshold voltage value.
 20. The dual-fuel heater according to claim 18, wherein when the selector valve is in the second position and the second gas is delivered only to the second thermocouple, the second thermocouple produces a voltage that is equal to or greater than the engagement threshold voltage value.
 21. The dual-fuel heater according to claim 12, wherein the engagement threshold value is about 4 mV.
 22. The dual-fuel heater according to claim 12, wherein the disengagement threshold value is about 1 mV. 